Luminescent Lanthanide Complexes for Effective Oxygen-Sensing and Singlet Oxygen Generation

Oxygen quantification using luminescence has attracted considerable attention in various fields, including environmental monitoring and clinical analysis. Among the reported luminophores, trivalent lanthanide complexes have displayed characteristic narrow emission bands with high brightness. This bright emission is based on photo-sensitized energy transfer via organic triplet states. The organic triplet states in lanthanide complexes effectively react with the triplet oxygen, enabling oxygen quantification by lanthanide luminescence. Some Tb^III and Eu^III complexes with slow deactivation processes have also formed the excited state equilibrium, thus resulting in the emission-lifetime based oxygen sensing property. The combination of Tb^III /Eu^III emission, Eu^III /Sm^III emission, Eu^III /ligand phosphorescence, and ligand fluorescence/ligand phosphorescence provide the ratiometric oxygen-sensing properties. Moreover, the reaction generates singlet oxygen species which exhibit numerous applications in the photo-medical field. The ligands with large π-conjugated aromatic systems, such as porphyrin, phthalocyanine, and polyaromatic compounds, induces highly efficient oxygen generation. The combination of effective luminescence with singlet-oxygen generation by the lanthanide complexes render them suitable for photo-driven theranostics. This review summarizes the research progress of lanthanide complexes with efficient oxygen-sensing and singlet-oxygen generation properties.

Tb3+ Photophysics: Mapping Excited State Dynamics of [Tb(H2O)9]3+ Using Molecular Photophysics

The study of optical transitions in lanthanide(III) ions has evolved separately from molecular photophysics, but the framework still applies to these forbidden transitions. In this study, a detailed photophysical characterization of the [Tb(H₂O)₉]³⁺ aqua ion was performed. The luminescence quantum yield (Φ_lum), excited state lifetime (τ_obs), radiative (k_r ≡ A) and nonradiative (k_nr) rate constants, and oscillator strength (f) were determined for Tb(CF₃SO₃)₃ in H₂O/D₂O mixtures in order to map the radiative and nonradiative transition probabilities. It was shown that the intense luminescence observed from Tb³⁺ compared to other Ln³⁺ ions is not due to a higher transition probability of emission but rather due to a lack of quenching, quantified by quenching to O-H oscillators in the aqua ion of k_q(OH) = 2090 s^-1 for terbium and k_q(OH) = 8840 s^-1 for europium. In addition, the Horrocks method of determining inner-sphere solvent molecules has been revisited, and it was concluded that the Tb³⁺ is 9-coordinated in aqueous solution.

A Tb3+ functionalized triazine-porous organic framework as a ratiometric fluorescent sensor for determination of ciprofloxacin in aquatic products

A Tb3+ functionalized triazine-porous organic framework (Tb3+/TAPOF) was prepared by introducing Tb3+ into a triazine-porous organic framework through a coordination bond.